mfd: intel-m10-bmc: Rename the local variables

Local variables directly interact with dev_get_drvdata/dev_set_drvdata
should be named ddata.

Reviewed-by: Russ Weight <russell.h.weight@intel.com>
Reviewed-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230116100845.6153-4-ilpo.jarvinen@linux.intel.com